If you really care about your friend better to tell him everything, and teach them how to play in the market. Im not saying that you idea is illegal, its legal as long as you are committed but again teaching him about cryptocurrency is the best thing that you can do, let him enjoy the cryptomarket.
Its much better, he won't ask for your help at another time after you tell him about anything, how to buy, about the bitcoin market, and so on. tell him everything, and he will buy it himself, its much better I think